1. Field of the Invention
The present invention relates to an organic light emitting display (OLED) and a method of fabricating the same and, more particularly, to an OLED including first and second substrates attached with each other, each of which emits different colors.
2. Discussion of the Background
Generally, a cathode ray tube (CRT) is often used for a TV monitor, measuring equipment, or an information terminal. However, the CRT is not used with small and lightweight electronic products due to its weight and size.
Thin and lightweight flat panel displays (FPD) are being substituted for CRTs. Such flat panel displays generally include a liquid crystal display (LCD), an OLED, etc.
A FPD may be a passive matrix FPD or an active matrix FPD according to its driving method.
The active matrix FPD includes a thin film transistor (TFT) substrate having a TFT formed therein, and red, green and blue light emitting diodes.
The active matrix FPD generally include at least two TFTs, i.e., a switching TFT and a driving TFT, a capacitor, and a light emitting diode (LED) in each pixel.
However, with top and bottom emitting active matrix FPDs, since the TFT and the capacitor occupy a relatively large area, less space is available for forming the LED, which reduces the aperture ratio.
Additionally, in order to increase the mobility of a TFT active layer, the TFT's size may be increased, which means it occupies a larger area in the pixel.
FIG. 1 is a cross-sectional view of a conventional OLED.
Referring to FIG. 1, a buffer layer 110 having a predetermined thickness is formed on a transparent insulating substrate 100 having red (A), green (B) and blue (C) pixel regions. The buffer layer 110 prevents impurities from the transparent insulating layer 100 from being introduced into the TFT, which is subsequently formed.
Next, polysilicon layer patterns 120 are formed on the buffer layer 110, and impurities are injected into both sides of the polysilicon layer patterns 120, thereby forming source and drain regions 122 and 124, and channel regions 126 between the source and drain regions, in each pixel region A, B and C.
Next, a gate insulating layer 130 is formed on the entire surface of the resultant structure, and gate electrodes 132 are then formed to correspond to the channel regions 126 of the polysilicon layer patterns 120.
Next, an interlayer insulating layer 140 is formed on the entire surface of the resultant structure, and the interlayer insulating layer 140 and the gate insulating layer 130 are etched to form contact holes 142, which expose the source and drain regions 122 and 124. Source and drain electrodes 150 and 152 are then formed to be connected with the source and drain regions 122 and 124, respectively, through the contact holes 142.
Next, a passivation layer 160 and a planarization layer 170 are formed on the entire surface of the resultant structure.
The passivation layer 160 and the planarization layer 170 are then etched to form via-holes 172, which expose the drain electrodes 152.
Next, pixel electrodes 180 are formed to be connected with the drain electrodes 152 through the via-holes 172 in each pixel region A, B and C. The pixel electrode 180 may be a reflective electrode.
Portions of the pixel electrodes 180 are then exposed on the entire surface of the resultant structure to form a pixel defining layer pattern 182 for defining an emission region.
Next, an organic layer 190, which includes at least an emission layer, and an opposite electrode 192 are formed on the entire surface of the resultant structure. The organic layer 190 may include an emission layer that emits blue or white light.
A transparent passivation layer (not shown) is then formed on the opposite electrode 192.
A sealing substrate 200 is adhered corresponding to the transparent insulating substrate 100 to complete the OLED. A moisture absorbing agent may be formed on the sealing substrate 200.
As described above, since the conventional OLED includes a plurality of pixel regions formed in one insulating substrate, as higher resolution and brightness are required, pixel patterning may become difficult. Further, with the active matrix OLED, the aperture ratio and the OLED's lifespan may decrease since the TFT and capacitor are formed in each pixel.